Heterobasidion Is a Basidiomycete That Contributes to Mortality of Trees

Heterobasidion is a basidiomycete that contributes to mortality of trees. Kuhlman isolated 23 strains of Heterobasidion and applied them to 16 seedlings of 10 different tree species. Partial results of this experiment are shown in the table. (From Kuhlman, E. G. 1970. Seedling inoculations with Fomes annosus show variation in virulence and in host susceptibility. Phytopathology 60:1743-1746. https://www.apsnet.org/publications/phytopathology/backissues/Documents/1970Articles/Phyto60n12_1743.PDF)
% mortality of five host species from five Heterobasidion isolates
$$\begin{array} { | l | l | l | l | l | l | } \hline & \text { Isolate } & \text { Isolate } & \text { Isolate } & \text { Isolate } & \text { Isolate } \\\hline \text { Host } & 63 & 117 & 195 & 126 & 118 \\\hline \text { Slash Pine } & 50 & 69 & 94 & 100 & 94 \\\hline \text { Shortleaf Pine } & 75 & 56 & 94 & 94 & 100 \\\hline \text { Red Cedar } & 38 & 32 & 19 & 50 & 25 \\\hline \text { Yellow-Poplar } &0 & 0 & 6 & 6 & 6 \\\hline \text { Sycamore } & 0 & 0 & 0 & 0 & 6 \\\hline\end{array}$$
-Which of the following conclusions can best be drawn from these results?

A) All tree species are susceptible to Heterobasidion.
B) Heterobasidion strains are equally lethal to all tree species.
C) Heterobasidion reduces mortality of some species.
D) Tree species vary in their susceptibility to Heterobasidion.